In closed piston, three-passage torque converters, the clutch piston divides the cooling oil circuit and the apply circuit. The piston has large seals at its inside diameter (ID) and outside diameter (OD). These seals are designed for axially directed movement of the piston, but are not durable to rotation about the central axis of rotation. As engine torsionals act directly on the outer mating components of these seals, but not on the piston itself, the piston inertia creates a driving force counter to that of the outer mating components, which results in rotation relative to these components. Consequently, the torque converter generally includes a means for preventing this relative rotation.
In prior designs, the rotation is prevented via a splined engagement. Pistons are generally made of die-cast aluminum and have precision splines formed on their ID. The splines engage mating external splines formed into a forged hub member attached to the cover of the converter. Unfortunately, this splined arrangement is costly, difficult to implement on a stamped piston, and is prone to rattle. Rattling is particularly an issue on large diesel engines.
Thus, there is a long-felt need for an anti-rotation mechanism for a closed piston, three-passage torque converter that does not rattle.
There is also a long-felt need for an anti-rotation mechanism for a closed piston, three-passage torque converter that is cost effective and may be implemented on a stamped piston.
There is also a long-felt need for an anti-rotation mechanism for a closed piston, three-passage torque converter that mitigates or eliminates rattling during operation.